修回日期: 2013-02-05
接受日期: 2013-02-20
在线出版日期: 2013-03-18
Lgr5(leucine-rich repeat-containing g-protein coupled receptor 5)属于G蛋白耦联受体家族, 含17个富含亮氨酸重复序列和7次a螺旋跨膜区, 其N-和C-末端尾部侧翼富含半胱氨酸序列, 可在胃肠道、毛囊等多种组织中表达. Lgr5是最新发现的Wnt通路的靶基因, 而且是潜在的结肠癌干细胞标志物, 与结肠癌的发生和发展密切相关, 现就Lgr5与结肠癌的关系作一综述.
引文著录: 陈小燕, 赵逵. Lgr5与结肠癌关系的研究进展. 世界华人消化杂志 2013; 21(8): 673-678
Revised: February 5, 2013
Accepted: February 20, 2013
Published online: March 18, 2013
Leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5), a member of the G protein-coupled receptor family, contains 17 leucine-rich repeats and N- and C-terminal cysteine-rich flanking domains. Lgr5 is a marker for stem cells in the stomach, small intestine, colon, and hair follicles. Recently, Lgr5 has been identified as a target of Wnt signaling. As a potential marker for colorectal cancer stem cells, Lgr5 might be responsible for the initiation and progression of colorectal cancer. In this article we review recent progress in understanding the relationship between Lgr5 and colorectal cancer.
- Citation: Chen XY, Zhao K. Progress in understanding the relationship between Lgr5 and colorectal cancer. Shijie Huaren Xiaohua Zazhi 2013; 21(8): 673-678
- URL: https://www.wjgnet.com/1009-3079/full/v21/i8/673.htm
- DOI: https://dx.doi.org/10.11569/wcjd.v21.i8.673
结肠癌是胃肠道中最常见的恶性肿瘤之一, 居全球肿瘤发病率的第3位[1], 但其发病机制尚不明确. 新近研究表明Lgr5(leucine-rich repeat-containing g-protein coupled receptor 5)是Wnt通路的目标基因, 与R-脊椎蛋白(R-spondins, RSPOs)结合能够增强Wnt/β-catenin信号, 进而参与结肠癌等肿瘤的发生. 许多研究发现Lgr5+干细胞是结肠癌的起始细胞, 作为潜在的结肠癌干细胞标志物的Lgr5在结肠癌中大量表达, 并与结肠癌的转移、复发以及患者的预后密切相关. 本文将系统阐述Lgr5与结肠癌发生发展关系的研究进展.
Lgr5, 又名GPR49、HG38、FEX、GPR67和MGC117008, 是7次跨膜(seven-transmembrane, TM)蛋白, 属于G蛋白耦联受体(G-protein-coupled receptors, GPCRS)家族的成员, 其胞外区含有与糖蛋白配体作用的17个富含亮氨酸重复序列, 7次α螺旋跨膜区高度保守, N-端和C-端尾部侧翼富含半胱氨酸序列. 最初因未发现其生理性配体, 故称为孤儿受体. 目前研究发现Lgr5的配体为R-脊椎蛋白, 两者的结合能够增强Wnt/β-catenin信号, 并对干细胞生长起多效作用[2]. Lgr蛋白通过其胞外的N-端与R-脊椎蛋白结合, 但是现有证据指出其并不利用G蛋白[2,3]. Lgr5与G蛋白偶联受体相关, 例如促甲状腺激素(thyroid-stimulating hormone, TSH)、卵泡刺激素(follicle-stimulating hormone, FSH)及促黄体激素(luteinizing hormone, LH). 这些激素受体在胞外N-端富含亮氨酸并含有9个与糖蛋白激素相结合的重复单位. DNA的杂交分析表明Lgr5基因在哺乳动物的进化中高度保守. 人类lgr5基因定位于染色体12q22-23, cDNA全长4 208 bp, 含有22个外显子和21个内含子, 转录产生8个不同的mRNA, 其中5个为选择性剪切体, 可读框编码由907个氨基酸残基组成的多肽链, 其中信号肽21个, 外功能区540个, 跨膜区263个, C-端尾部83个. 相比TSH等糖蛋白激素的限制性表达, Lgr5可在多种组织中表达, 例如骨骼肌[4]、胃肠道[5]、毛囊[6-8]、大脑[9]、脊髓、乳腺[10]、眼睛及生殖器官等.
在关于结肠癌的研究中发现Lgr5是许多自我更新组织包括肠道和毛囊等的干细胞标志物, 而且是与结肠癌发生密切相关的Wnt通路的靶基因[5,11,12]. Wnt信号诱导Axin与磷酸化的LRP结合, 降解复合体分离, β-catenin在胞浆中稳定存在并转位入核, 与Tcf/Lef结合, 形成转录复合体, 激活Lgr5及gastrin等靶基因的转录[13,14]. Lgr5家族可介导R-脊椎蛋白参与Wnt经典信号通路[15,16], 并证实Lgr受体与R-脊椎蛋白密切结合, 即使是少量Wnt信号刺激时也能够增强Wnt的信号作用, 进而参与肿瘤的发生. Carmon等[17]关于Lgr5与Wnt受体的相互作用的研究表明, Lgr5是Wnt信号复合体的一部分, 并在膜水平增强Wnt/β-catenin信号. Fan等[18]运用免疫组织化学检测102例结肠癌患者中Lgr5和β-catenin的表达, 结果显示, Lgr5与β-catenin的表达呈正相关, 由此推测Lgr5可能通过 Wnt/β-catenin通路参与结肠癌的发生. Barker等[12]通过消除Lgr5-cre阳性表达小鼠肠干细胞的APC基因, 3-5 wk后发生转变的肠干细胞仍存留在隐窝底部, 并形成由微腺瘤到肉眼可见的Lgr5+的腺瘤, 并伴有细胞核内β-catenin高表达, 这说明Lgr5可促进β-catenin表达, 启动Wnt通路. 关于Lgr5是如何增强Wnt信号的机制依然不清楚[3]. 然而, 一些学者却提出了相反的观点, 认为Lgr5非但不能增强Wnt信号, 反而起负性调节作用. Walker等[19]通过RNA干扰技术调控Lgr5的表达, 发现Lgr5的表达减少会诱导肿瘤侵袭和锚地依赖性生长以及致瘤性增强. 相反, Lgr5的过表达导致细胞黏附增强, 集落生成及致瘤性减弱. 表达谱同样显示, 基因敲出Lgr5的细胞使Wnt信号增强和EMT基因上调, 这与Lgr5高表达细胞中改变是相反的. 由此证实在结肠癌细胞株中, Lgr5拮抗Wnt信号和调控细胞黏附, 负性调节肿瘤的发展. Garcia等[20]关于Lgr5对胚胎期小肠上皮发育的作用的研究也发现Lgr5基因敲除导致了Wnt通路靶基因的过度表达, 进一步证实了Lgr5作为Wnt信号通路的负调控因子. 此外, 有研究显示肿瘤坏死因子受体家族成员-Troy, 可抑制Lgr5+肠道干细胞中Wnt信号转导[21].
结肠黏膜上皮的再生, 是通过位于结肠隐窝基底部潘氏细胞之间的肠干细胞(intestinal stem cells, ISCs)而维持. ISCs的特点就是Lgr5高表达, 对Wnt信号的调节非常敏感. ISCs的后代被称为短暂扩充(transient amplifying, TA)细胞, 经数次有丝分裂并沿着隐窝轴向上迁移而得到扩充. TA细胞离开隐窝向肠腔靠近时, TA细胞经历细胞周期阻滞和终末分化. 最近的研究采用生物标志物技术以便更准确地评估这些干细胞在肠隐窝的定位. 这些新的标记中, 最值得注意的是Lgr5. Lgr5是ISCs分裂活跃的标志[22]. 鼠的小肠[23]、结肠[12]和胃[3]的干细胞均可特异性表达Lgr5. Lgr5+肠干细胞寿命长, 持续增殖并且能够分化为不同的终末分化上皮细胞类型, 包括吸收细胞、杯状细胞、肠内分泌细胞、帕内特细胞[24], 同时也能保持其干细胞状态. 单个Lgr5+隐窝干细胞在体外可以形成类器官结构, Yui等[25]将一个Lgr5+结肠干细胞植入到小鼠结肠表面受损的GFP+细胞中以检测Lgr5+结肠干细胞的移植能力, 其结果发现, 4 wk后Lgr5+结肠干细胞形成单层上皮细胞, 并且还形成功能和组织学均正常的而且具有自我更新能力的肠隐窝, 6 mo之后, Lgr5+结肠干细胞在体外不断扩增形成了移植组织. Snippert等[26]通过运用多色的Cre重组酶受体对Lgr5+干细胞进行追踪发现肠隐窝动态平衡依赖于Lgr5+干细胞的对称分裂. Schepers等[27]再次运用谱系追踪小鼠肠腺瘤中Lgr5+干细胞活性发现, 占腺瘤细胞5%-10%的Lgr5+细胞产生额外的Lgr5+细胞以及所有其他腺瘤细胞类型, 并且加速腺瘤生长. 在大多数情况下, 肠道肿瘤的发生是受Wnt信号转导通路突变的驱动. 小鼠中, Lgr5+细胞比其他Wnt信号通路突变的肠上皮细胞群更容易引起肠道肿瘤[12]. 这一结果表明Lgr5+干细胞是结肠癌的起始细胞[28,29]. 换言之, Lgr5是结肠癌干细胞的标志物[30].
已经证实在人类多种类型的肿瘤中[31-33], 例如卵巢瘤、脑胶质瘤等, 特别是结肠癌[34], 可见Lgr5的高表达. 由Lgr5在肠腺瘤中限制性表达的模式推测: Lgr5可能在结肠癌干细胞中也是选择性表达. Takahashi等[35]随后报道了Lgr5限制性表达通常在人腺瘤细胞的基底层, 肿瘤和间质细胞的交界处. Becker等[36]运用免疫组织化学的方法比较正常结肠、癌前病变以及结肠腺瘤Lgr5的表达发现, 正常的组织中Lgr5在隐窝基底部表达, 而在癌前病变的组织中Lgr5的表达并不局限于隐窝基底部且表达量较高, 结肠腺瘤中Lgr5较少在基底部表达, 而是在腺腔的表面大量表达. 此研究表明Lgr5是人肠道干细胞的一个潜在标志物, 其失巢表达是干细胞向癌前病变转变的早期事件, 并在肿瘤的发生中起重要作用. Takeda等[37]也采用免疫组织化学对17例低分化和13例高分化的腺瘤以及30例腺癌分析Lgr5的表达, 结果显示腺瘤中, Lgr5的表达部位与肿瘤分化有关, 在腔面表达与分化呈负相关, 然而隐窝部表达与分化呈正相关; 腺癌中, Lgr5的表达部位与肿瘤分期有关, 在腔面表达与分期呈负相关, 隐窝部表达与分期呈正相关, 进一步表明结肠癌发生的各个阶段中, Lgr5的空间分布存在着明显的差异, 这与Simon等[38]的研究不谋而合. 此外, Amsterdam等[39]研究同样发现, 在正常组织中, 只在隐窝有散在的Lgr5+细胞, 胞膜和胞浆均有染色; 在癌旁组织中, 隐窝部位Lgr5+细胞更密集, 包括上皮细胞都有着色; 在癌组织中, Lgr5+细胞主要集中在低分化肿瘤中, 而高分化的肿瘤只散在分布着Lgr5+细胞. 许多研究表明Lgr5在癌组织及癌旁组织大量表达, 但Uchida等[33]的研究显示, Lgr5在肿瘤间质中不表达, 这与Takahashi等[35]报道相一致. 以上的研究均表明, Lgr5的表达定位与结肠癌发生发展密切相关.
Lgr5在多种类型的癌症中都过度表达, 并能促进的肿瘤细胞的增长和转移[31,32,40,41]. 研究表明, 在转移性结肠癌细胞系中, Lgr5的表达较高. Kleist等[42]比较原发性结肠癌和转移性结肠癌的Lgr5的表达发现, 后者的Lgr5表达水平远超过前者. Uchida等[33]对结肠癌Lgr5的表达与其临床病理意义进行评估, 结果显示Lgr5蛋白表达水平与淋巴结转移、淋巴管浸润、血管浸润及肿瘤分期呈正相关, 而与患者年龄、性别、肿瘤的分化程度、位置及大小无明显相关, 这与付焱等[43]的研究结果相似. 但是Wu等[44]为了确定Lgr5是否是一个潜在的结肠癌干细胞的标志物以及其与患者预后是否相关, 检测结肠癌中Lgr5与Ki-67在大肠癌中的表达, 发现Lgr5的表达不仅与浸润深度、淋巴结转移以及远处转移有关, 而且与组织学分级亦呈正相关, 结果还表明Lgr5是作为一个独立的影响结肠癌患者预后的因素. 这与Takahashi等[35]的研究结果相一致, 也显示Lgr5表达可能是大肠癌患者的不良预后因素. Saigusa等[45,46]采用实时定量PCR技术测定术前放化疗后直肠癌患者的Lgr5基因表达水平, 发现Lgr5基因高表达, 其无病生存期越短, 两者呈正相关. 上述结果均表明Lgr5过表达可能促进肿瘤的转移, 对结肠癌的进展发挥重要作用, 由此表明Lgr5可以作为一个判断结肠癌患者预后的指标, 是一个潜在的结肠癌治疗新靶点.
许多作者认为Lgr5可以作为结肠癌干细胞最为理想的标志物之一[42,47]. Kemper等[48]甚至认为Lgr5不仅可以作为一个肠干细胞的生物学和功能性标志物, 而且是结肠癌干细胞的选择标志物. 鉴于Lgr5对结肠癌的发生和发展有重要作用, 因此越来越多的研究学者更迫切希望对Lgr5+的结肠癌干细胞进行研究, 以便对其有更为深入的了解. 那么如何分选Lgr5+的结肠癌干细胞呢? 我们可以通过分选SP(side population, SP)细胞以及悬浮培养法分离肿瘤干细胞, 但是上述两种方法只能够富集包括Lgr5+细胞在内的肿瘤干细胞, 而不能直接分选出Lgr5+的结肠癌干细胞. 因此, 只有应用细胞表面特异性标志进行分选.
研究发现结肠癌干细胞较已分化的肿瘤干细胞相比, Wnt信号更强, 表明可以用Wnt信号强度来识别干细胞, 因此有人猜想可以通过构建Wnt的受体来分离结肠癌干细胞[49]. 但是结肠癌干细胞中Wnt信号增强的表现就是核β-catenin升高, 显然基于β-catenin的方法是不可行的. Lgr5是一个7个跨膜糖蛋白, 关于其在细胞的定位仍存在着较大争议, 通过免疫组织化学或免疫荧光技术发现Lgr5在胞膜上或胞质中亦或是胞膜上和胞质中都有表达, 原因主要在于现有抗体对Lgr5抗原表位的识别. 要通过细胞表面特异性标记法运用荧光激活细胞分选术(fluorescence-activated cell sorting, FACS)又称流式细胞技术或磁珠分选技术, 需要该抗体识别Lgr5的胞外部分. 然而, 到目前为止, 已发现多种Lgr5的抗体, 但都不能用于FACS分析.
King等[50]一系列的研究表明CD24在肠道的空间分布与Lgr5极其相似, 于是推测通过膜蛋白CD24可以分离Lgr5+结肠上皮干细胞, 他们用FACS检测发现, Lgr5-EGFP小鼠中CD24+细胞中含有大部分Lgr5+结肠上皮干细胞. 最近, Kemper等[48]针对Lgr5设计出3种新的单克隆抗体, 通过无血清方法富集结肠癌干细胞之后再进行流式分选, 但需同时加入3种Lgr5抗体, 在Epcam+细胞中Lgr5+细胞比例在1.9%-11.1%之间. 然而这3种抗体运用还不够成熟, 流式分选时所需抗体多, 成本高, 而且不能用于Lgr5的Western blot和免疫组织化学检测. 因此, 我们的建议是最好先经无血清培养法富集肿瘤干细胞, 再运用FACS技术经CD24间接分选出Lgr5+结肠癌细胞.
Lgr5属于G蛋白耦联受体家族, 含17个富含亮氨酸重复序列和7次α螺旋跨膜区, 可在胃肠道、毛囊等多种组织中表达. Lgr5是最新发现的Wnt通路的靶基因, 而且是潜在的结肠癌干细胞标志物, 与结肠癌的发生和发展密切相关, 本文主要介绍Lgr5与结肠癌关系的研究进展.
赵青川, 教授, 主任医师, 西京医院消化外科
许多研究发现Lgr5+干细胞是结肠癌的起始细胞, 作为潜在的结肠癌干细胞标志物的Lgr5在结肠癌中大量表达, 并与结肠癌的转移、复发以及患者的预后密切相关, 表明其可作为结肠癌治疗的一个潜在靶点.
Becker等报道了Lgr5是人肠道干细胞的一个潜在标志物, 其表达异常是干细胞向癌前病变转变的早期事件, 并在肿瘤的发生中起重要作用.
本文总结了Lgr5与结肠癌的关系, 如与Wnt/β-catenin通路、结肠癌干细胞、结肠癌患者预后等, 并提出了关于Lgr5+结肠癌干细胞分选的相关问题.
Lgr5: 又名为GPR49、HG38、FEX、GPR67和MGC117008, 是一个7次跨膜(TM)蛋白, 属于G蛋白耦联受体(GPCRS)家族的成员, 其胞外区含有与糖蛋白配体作用的17个富含亮氨酸重复序列, 7次α螺旋跨膜区高度保守, N-端和C-端尾部侧翼富含半胱氨酸序列. 最初因未发现其生理性配体, 故称为孤儿受体.
本文针对Lgr5的结构和功能进行了综述, 标志物与结肠癌的发生和发展密切相关. 这些进展的介绍有利于读者获取新知识, 为结肠癌的研究提供了新的思路.
编辑: 田滢 电编: 闫晋利
| 1. | Grizzi F, Celesti G, Basso G, Laghi L. Tumor budding as a potential histopathological biomarker in colorectal cancer: hype or hope? World J Gastroenterol. 2012;18:6532-6536. [PubMed] [DOI] |
| 2. | Carmon KS, Gong X, Lin Q, Thomas A, Liu Q. R-spondins function as ligands of the orphan receptors LGR4 and LGR5 to regulate Wnt/beta-catenin signaling. Proc Natl Acad Sci U S A. 2011;108:11452-11457. [PubMed] [DOI] |
| 3. | de Lau W, Barker N, Low TY, Koo BK, Li VS, Teunissen H, Kujala P, Haegebarth A, Peters PJ, van de Wetering M. Lgr5 homologues associate with Wnt receptors and mediate R-spondin signalling. Nature. 2011;476:293-297. [PubMed] [DOI] |
| 4. | Rot S, Taubert H, Bache M, Greither T, Würl P, Eckert AW, Schubert J, Vordermark D, Kappler M. A novel splice variant of the stem cell marker LGR5/GPR49 is correlated with the risk of tumor-related death in soft-tissue sarcoma patients. BMC Cancer. 2011;11:429. [PubMed] [DOI] |
| 5. | Barker N, Huch M, Kujala P, van de Wetering M, Snippert HJ, van Es JH, Sato T, Stange DE, Begthel H, van den Born M. Lgr5(+ve) stem cells drive self-renewal in the stomach and build long-lived gastric units in vitro. Cell Stem Cell. 2010;6:25-36. [PubMed] |
| 6. | Plaks V, Brenot A, Lawson DA, Linnemann JR, Van Kappel EC, Wong KC, de Sauvage F, Klein OD, Werb Z. Lgr5-expressing cells are sufficient and necessary for postnatal mammary gland organogenesis. Cell Rep. 2013;3:70-78. [PubMed] [DOI] |
| 7. | da Silva-Diz V, Solé-Sánchez S, Valdés-Gutiérrez A, Urpí M, Riba-Artés D, Penin RM, Pascual G, González-Suárez E, Casanovas O, Viñals F. Progeny of Lgr5-expressing hair follicle stem cell contributes to papillomavirus-induced tumor development in epidermis. Oncogene. 2012; Sep 3. [Epub ahead of print]. [PubMed] [DOI] |
| 8. | Mardaryev AN, Meier N, Poterlowicz K, Sharov AA, Sharova TY, Ahmed MI, Rapisarda V, Lewis C, Fessing MY, Ruenger TM. Lhx2 differentially regulates Sox9, Tcf4 and Lgr5 in hair follicle stem cells to promote epidermal regeneration after injury. Development. 2011;138:4843-4852. [PubMed] [DOI] |
| 9. | Nakata S, Campos B, Bageritz J, Bermejo JL, Becker N, Engel F, Acker T, Momma S, Herold-Mende C, Lichter P. LGR5 is a marker of poor prognosis in glioblastoma and is required for survival of brain cancer stem-like cells. Brain Pathol. 2013;23:60-72. [PubMed] [DOI] |
| 10. | de Visser KE, Ciampricotti M, Michalak EM, Tan DW, Speksnijder EN, Hau CS, Clevers H, Barker N, Jonkers J. Developmental stage-specific contribution of LGR5(+) cells to basal and luminal epithelial lineages in the postnatal mammary gland. J Pathol. 2012;228:300-309. [PubMed] [DOI] |
| 11. | Ruffner H, Sprunger J, Charlat O, Leighton-Davies J, Grosshans B, Salathe A, Zietzling S, Beck V, Therier M, Isken A. R-Spondin potentiates Wnt/β-catenin signaling through orphan receptors LGR4 and LGR5. PLoS One. 2012;7:e40976. [PubMed] [DOI] |
| 12. | Barker N, Ridgway RA, van Es JH, van de Wetering M, Begthel H, van den Born M, Danenberg E, Clarke AR, Sansom OJ, Clevers H. Crypt stem cells as the cells-of-origin of intestinal cancer. Nature. 2009;457:608-611. [PubMed] |
| 13. | Clevers H, Nusse R. Wnt/β-catenin signaling and disease. Cell. 2012;149:1192-1205. [PubMed] [DOI] |
| 14. | MacDonald BT, Tamai K, He X. Wnt/beta-catenin signaling: components, mechanisms, and diseases. Dev Cell. 2009;17:9-26. [PubMed] [DOI] |
| 15. | Glinka A, Dolde C, Kirsch N, Huang YL, Kazanskaya O, Ingelfinger D, Boutros M, Cruciat CM, Niehrs C. LGR4 and LGR5 are R-spondin receptors mediating Wnt/β-catenin and Wnt/PCP signalling. EMBO Rep. 2011;12:1055-1061. [PubMed] [DOI] |
| 16. | de Lau W, Barker N, Low TY, Koo BK, Li VS, Teunissen H, Kujala P, Haegebarth A, Peters PJ, van de Wetering M. Lgr5 homologues associate with Wnt receptors and mediate R-spondin signalling. Nature. 2011;476:293-297. [PubMed] [DOI] |
| 17. | Carmon KS, Lin Q, Gong X, Thomas A, Liu Q. LGR5 interacts and cointernalizes with Wnt receptors to modulate Wnt/β-catenin signaling. Mol Cell Biol. 2012;32:2054-2064. [PubMed] [DOI] |
| 18. | Fan XS, Wu HY, Yu HP, Zhou Q, Zhang YF, Huang Q. Expression of Lgr5 in human colorectal carcinogenesis and its potential correlation with beta-catenin. Int J Colorectal Dis. 2010;25:583-590. [PubMed] [DOI] |
| 19. | Walker F, Zhang HH, Odorizzi A, Burgess AW. LGR5 is a negative regulator of tumourigenicity, antagonizes Wnt signalling and regulates cell adhesion in colorectal cancer cell lines. PLoS One. 2011;6:e22733. [PubMed] [DOI] |
| 20. | Garcia MI, Ghiani M, Lefort A, Libert F, Strollo S, Vassart G. LGR5 deficiency deregulates Wnt signaling and leads to precocious Paneth cell differentiation in the fetal intestine. Dev Biol. 2009;331:58-67. [PubMed] [DOI] |
| 21. | Fafilek B, Krausova M, Vojtechova M, Pospichalova V, Tumova L, Sloncova E, Huranova M, Stancikova J, Hlavata A, Svec J. Troy, a Tumor Necrosis Factor Receptor Family Member, Interacts With Lgr5 to Inhibit Wnt Signaling in Intestinal Stem Cells. Gastroenterology. 2012; Nov 7. [Epub ahead of print]. [PubMed] [DOI] |
| 22. | Yan KS, Chia LA, Li X, Ootani A, Su J, Lee JY, Su N, Luo Y, Heilshorn SC, Amieva MR. The intestinal stem cell markers Bmi1 and Lgr5 identify two functionally distinct populations. Proc Natl Acad Sci U S A. 2012;109:466-471. [PubMed] [DOI] |
| 23. | Barker N, van Es JH, Kuipers J, Kujala P, van den Born M, Cozijnsen M, Haegebarth A, Korving J, Begthel H, Peters PJ. Identification of stem cells in small intestine and colon by marker gene Lgr5. Nature. 2007;449:1003-1007. [PubMed] |
| 24. | Gerbe F, van Es JH, Makrini L, Brulin B, Mellitzer G, Robine S, Romagnolo B, Shroyer NF, Bourgaux JF, Pignodel C. Distinct ATOH1 and Neurog3 requirements define tuft cells as a new secretory cell type in the intestinal epithelium. J Cell Biol. 2011;192:767-780. [PubMed] [DOI] |
| 25. | Yui S, Nakamura T, Sato T, Nemoto Y, Mizutani T, Zheng X, Ichinose S, Nagaishi T, Okamoto R, Tsuchiya K. Functional engraftment of colon epithelium expanded in vitro from a single adult Lgr5* stem cell. Nat Med. 2012;18:618-623. [PubMed] [DOI] |
| 26. | Snippert HJ, van der Flier LG, Sato T, van Es JH, van den Born M, Kroon-Veenboer C, Barker N, Klein AM, van Rheenen J, Simons BD. Intestinal crypt homeostasis results from neutral competition between symmetrically dividing Lgr5 stem cells. Cell. 2010;143:134-144. [PubMed] [DOI] |
| 27. | Schepers AG, Snippert HJ, Stange DE, van den Born M, van Es JH, van de Wetering M, Clevers H. Lineage tracing reveals Lgr5+ stem cell activity in mouse intestinal adenomas. Science. 2012;337:730-735. [PubMed] [DOI] |
| 28. | Sato T, Vries RG, Snippert HJ, van de Wetering M, Barker N, Stange DE, van Es JH, Abo A, Kujala P, Peters PJ. Single Lgr5 stem cells build crypt-villus structures in vitro without a mesenchymal niche. Nature. 2009;459:262-265. [PubMed] |
| 29. | Schuijers J, Clevers H. Adult mammalian stem cells: the role of Wnt, Lgr5 and R-spondins. EMBO J. 2012;31:2685-2696. [PubMed] [DOI] |
| 30. | Leushacke M, Barker N. Lgr5 and Lgr6 as markers to study adult stem cell roles in self-renewal and cancer. Oncogene. 2012;31:3009-3022. [PubMed] |
| 31. | McClanahan T, Koseoglu S, Smith K, Grein J, Gustafson E, Black S, Kirschmeier P, Samatar AA. Identification of overexpression of orphan G protein-coupled receptor GPR49 in human colon and ovarian primary tumors. Cancer Biol Ther. 2006;5:419-426. [PubMed] |
| 32. | Tanese K, Fukuma M, Yamada T, Mori T, Yoshikawa T, Watanabe W, Ishiko A, Amagai M, Nishikawa T, Sakamoto M. G-protein-coupled receptor GPR49 is up-regulated in basal cell carcinoma and promotes cell proliferation and tumor formation. Am J Pathol. 2008;173:835-843. [PubMed] [DOI] |
| 33. | Uchida H, Yamazaki K, Fukuma M, Yamada T, Hayashida T, Hasegawa H, Kitajima M, Kitagawa Y, Sakamoto M. Overexpression of leucine-rich repeat-containing G protein-coupled receptor 5 in colorectal cancer. Cancer Sci. 2010;101:1731-1737. [PubMed] [DOI] |
| 34. | Merlos-Suárez A, Barriga FM, Jung P, Iglesias M, Céspedes MV, Rossell D, Sevillano M, Hernando-Momblona X, da Silva-Diz V, Muñoz P. The intestinal stem cell signature identifies colorectal cancer stem cells and predicts disease relapse. Cell Stem Cell. 2011;8:511-524. [PubMed] [DOI] |
| 35. | Takahashi H, Ishii H, Nishida N, Takemasa I, Mizushima T, Ikeda M, Yokobori T, Mimori K, Yamamoto H, Sekimoto M. Significance of Lgr5(+ve) cancer stem cells in the colon and rectum. Ann Surg Oncol. 2011;18:1166-1174. [PubMed] [DOI] |
| 36. | Becker L, Huang Q, Mashimo H. Immunostaining of Lgr5, an intestinal stem cell marker, in normal and premalignant human gastrointestinal tissue. ScientificWorldJournal. 2008;8:1168-1176. [PubMed] [DOI] |
| 37. | Takeda K, Kinoshita I, Shimizu Y, Matsuno Y, Shichinohe T, Dosaka-Akita H. Expression of LGR5, an intestinal stem cell marker, during each stage of colorectal tumorigenesis. Anticancer Res. 2011;31:263-270. [PubMed] |
| 38. | Simon E, Petke D, Böger C, Behrens HM, Warneke V, Ebert M, Röcken C. The spatial distribution of LGR5+ cells correlates with gastric cancer progression. PLoS One. 2012;7:e35486. [PubMed] [DOI] |
| 39. | Amsterdam A, Raanan C, Schreiber L, Freyhan O, Fabrikant Y, Melzer E, Givol D. Differential localization of LGR5 and Nanog in clusters of colon cancer stem cells. Acta Histochem. 2012; Oct 23. [Epub ahead of print]. [PubMed] [DOI] |
| 40. | Gao Y, Kitagawa K, Hiramatsu Y, Kikuchi H, Isobe T, Shimada M, Uchida C, Hattori T, Oda T, Nakayama K. Up-regulation of GPR48 induced by down-regulation of p27Kip1 enhances carcinoma cell invasiveness and metastasis. Cancer Res. 2006;66:11623-11631. [PubMed] |
| 41. | Al-Kharusi MR, Smartt HJ, Greenhough A, Collard TJ, Emery ED, Williams AC, Paraskeva C. LGR5 promotes survival in human colorectal adenoma cells and is upregulated by PGE2: implications for targeting adenoma stem cells with NSAIDs. Carcinogenesis. 2013; Feb 13. [Epub ahead of print]. [PubMed] |
| 42. | Kleist B, Xu L, Li G, Kersten C. Expression of the adult intestinal stem cell marker Lgr5 in the metastatic cascade of colorectal cancer. Int J Clin Exp Pathol. 2011;4:327-335. [PubMed] |
| 44. | Wu XS, Xi HQ, Chen L. Lgr5 is a potential marker of colorectal carcinoma stem cells that correlates with patient survival. World J Surg Oncol. 2012;10:244. [PubMed] |
| 45. | Saigusa S, Inoue Y, Tanaka K, Toiyama Y, Kawamura M, Okugawa Y, Okigami M, Hiro J, Uchida K, Mohri Y. Significant correlation between LKB1 and LGR5 gene expression and the association with poor recurrence-free survival in rectal cancer after preoperative chemoradiotherapy. J Cancer Res Clin Oncol. 2013;139:131-138. [PubMed] [DOI] |
| 46. | Saigusa S, Inoue Y, Tanaka K, Toiyama Y, Matsushita K, Kawamura M, Okugawa Y, Hiro J, Uchida K, Mohri Y. Clinical significance of LGR5 and CD44 expression in locally advanced rectal cancer after preoperative chemoradiotherapy. Int J Oncol. 2012;41:1643-1652. [PubMed] [DOI] |
| 47. | Takahashi H, Ishii H, Nishida N, Takemasa I, Mizushima T, Ikeda M, Yokobori T, Mimori K, Yamamoto H, Sekimoto M. Significance of Lgr5(+ve) cancer stem cells in the colon and rectum. Ann Surg Oncol. 2011;18:1166-1174. [PubMed] |
| 48. | Kemper K, Prasetyanti PR, De Lau W, Rodermond H, Clevers H, Medema JP. Monoclonal antibodies against Lgr5 identify human colorectal cancer stem cells. Stem Cells. 2012;30:2378-2386. [PubMed] [DOI] |
| 49. | Vermeulen L, De Sousa E Melo F, van der Heijden M, Cameron K, de Jong JH, Borovski T, Tuynman JB, Todaro M, Merz C, Rodermond H. Wnt activity defines colon cancer stem cells and is regulated by the microenvironment. Nat Cell Biol. 2010;12:468-476. [PubMed] |
| 50. | King JB, von Furstenberg RJ, Smith BJ, McNaughton KK, Galanko JA, Henning SJ. CD24 can be used to isolate Lgr5+ putative colonic epithelial stem cells in mice. Am J Physiol Gastrointest Liver Physiol. 2012;303:G443-G452. [PubMed] |